1. Field of the Invention
This invention relates to alkali salts of a sulphonated styrene polymer or copolymer and the process for preparing the same. The invention also relates to the use of these alkali salts of a sulphonated styrene polymer or copolymer as fluidizing agents for use with mineral binders.
2. Description of the Prior Art
It is known that in order to bring mineral binders such as cement, lime hydraulic lime, plaster of anhydrite, used either alone or mixed with additives, into a form which makes it possible to work them, it is necessary to mix them with a proportion of water which appreciably exceeds that required by the mechanical reaction. It accordingly follows that after setting of the mineral binder has taken place, the excess water has to evaporate, which has the effect of leaving cavities in the constructional unit. These cavities considerably reduce the mechanical strength of the constructional unit.
It is likewise known that fluidizing agents of various forms may be advantageously incorporated with mineral binders. These fluidizing agents hve the dual function of serving to disperse the particles of the mineral binders as well as to finely distribute the air contained in the mixture, the air being entrapped in the course of handling and mixing the mineral binders. As a result of these two phenomena, there is brought about an improved liquification or flowability of the binders as well as an improved workability of the mineral binders.
There are presently available fluidizing agents which are known to exhibit the above fluidizing characteristics. Examples of these fluidizing agents are the sodium salts of condensation products of naphthalene-.beta.-sulphonic acid with formaldehyde, sodium laurylsulphate, the butyl ester of sulphonated ricinoleic acid or sulphated isobutyl oleate.
Unfortunately, all of these products have the inherent disadvantage of considerably decreasing the setting time of the mineral binders and may in fact tend to completely prevent setting. Likewise, these products have the effect of causing considerable sweating -- the binder no longer retains the water with which it was mixed -- thus adversely affecting the mechanical properties of the constructional unit.
There are also known to exist other fluidizing agents which are sulfide modified resins on a base of phenol/formaldehyde, melamine/formaldehyde or aminotriazine. These products have formed the subject of the following French Patents: Nos. 2,182,825 of Badische Aniline & Soda Fabrik, No. 1,510,314 of Suddeutsche Kalkstickstoff Werke, No. 1,570,149 of Hollfritsch, No. 2,042,860 and No. 2,059,288 of Hollfritsch.
While these products do not prevent setting of the mineral binder, their liquification power is weak and in certain cases they too give rise to sweating.